This invention relates to tubular locks and expandable keys of the type shown and described in Morse and Nielsen, U.S. Pat. No. 3,714,802; and in Hoyt, U.S. Pat. No. 3,835,674. These two patents illustrate the problem of making locks pick-resistant, and show two solutions which have proved less than entirely successful.
Locks for electric meter boxes have traditionally been openable only by keys provided to the utility companies by the lock makers. Special tubular locks have been openable only by special expandable keys. However, over the years, the special tubular locks have begun to be opened by unauthorized persons for the purpose of bypassing the meters (i.e. to obtain "free" electricity). Such illegal meter box openings are usually carried out in either of two ways.
First, the special expandable keys have fallen into unauthorized hands over the years. Obviously, such special keys can be used to open the special tubular locks that they were designed to open. Therefore, one object of this invention is to provide a modified lock which cannot be opened by the old style special expandable key. It is another object of this invention to provide a modified expandable key which can open the modified tubular lock, and which can also open the old style tubular lock.
Second, the special tubular locks can also be opened by picks, or by nails or screws driven into the tubular locks. These picks or nails or screws will wedge solidly in the moving parts of the lock, and the moving parts can then be retracted to open the lock. It is an object of this invention to provide a modified tubular lock that cannot be opened by such wedging tactics.
It is another object of this invention to provide a method for modifying conventional tubular locks and conventional expandable keys to fabricate the locks and keys of this invention.